// Простенький "селект билдер" по мотивам MediaWiki-овского, успешно юзаю подобный в PHP уже лет 8
// (c) Виталий Филиппов, 2019-2022
// Версия 2022-01-19

// В PHP, правда, прикольнее - там в массиве можно смешивать строковые и численные ключи,
// благодаря чему можно писать $where = [ 't1.a=t2.a', 't2.b' => [ 1, 2, 3 ] ]
// Здесь так нельзя, поэтому этот синтаксис мы заменяем на { 't1.a=t2.a': [], 't2.b': [ 1, 2, 3 ] }
// Или на [ 't1.a=t2.a', [ 't2.b', [ 1, 2, 3 ] ] ] - можно писать и так, и так

const pg = require('pg');
const pg_escape = require('pg-escape');

// Сраный node-postgres конвертирует даты в Date и портит таймзону

const DATATYPE_DATE = 1082;
const DATATYPE_TIME = 1083;
const DATATYPE_TIMESTAMP = 1114;
const DATATYPE_TIMESTAMPTZ = 1184;
const DATATYPE_TIMETZ = 1266;

pg.types.setTypeParser(DATATYPE_DATE, pgToString);
pg.types.setTypeParser(DATATYPE_TIME, pgToString);
pg.types.setTypeParser(DATATYPE_TIMESTAMP, pgToString);
pg.types.setTypeParser(DATATYPE_TIMESTAMPTZ, pgToString);
pg.types.setTypeParser(DATATYPE_TIMETZ, pgToString);

function pgToString(val)
{
    return val === null ? null : val;
}

const MS_HASH = 0;
const MS_LIST = 1;
const MS_ROW = 2;
const MS_COL = 4;
const MS_VALUE = 6;

function select_builder(tables, fields, where, options)
{
    options = options||{};
    let sql = 'SELECT ', bind = [];
    if (options['DISTINCT ON'] || options.distinct_on)
    {
        let group = options['DISTINCT ON'] || options.distinct_on;
        group = group instanceof Array ? group : [ group ];
        sql += 'DISTINCT ON ('+group.join(', ')+') ';
    }
    if (fields instanceof Array)
    {
        sql += fields.join(', ');
    }
    else if (typeof fields == 'string')
    {
        sql += fields;
    }
    else if (typeof fields == 'object')
    {
        sql += Object.keys(fields).map(k => fields[k]+' AS '+k).join(', ');
    }
    else
    {
        throw new Error('fields = '+fields+' is invalid');
    }
    sql += ' FROM ';
    const t = tables_builder(tables);
    sql += t.sql;
    t.bind.forEach(v => bind.push(v));
    where = where_builder(where);
    sql += ' WHERE '+(where.sql || '1=1');
    where.bind.forEach(v => bind.push(v));
    if (t.moreWhere)
    {
        sql += ' AND '+t.moreWhere.sql;
        t.moreWhere.bind.forEach(v => bind.push(v));
    }
    if (options['GROUP BY'] || options.group_by)
    {
        let group = options['GROUP BY'] || options.group_by;
        group = group instanceof Array ? group : [ group ];
        sql += ' GROUP BY '+group.join(', ');
    }
    if (options['ORDER BY'] || options.order_by)
    {
        let order = options['ORDER BY'] || options.order_by;
        order = order instanceof Array ? order : [ order ];
        sql += ' ORDER BY '+order.join(', ');
    }
    if (options.LIMIT || options.limit)
    {
        sql += ' LIMIT '+((options.LIMIT || options.limit) | 0);
    }
    if (options.OFFSET || options.offset)
    {
        sql += ' OFFSET '+((options.OFFSET || options.offset) | 0);
    }
    if (options['FOR UPDATE'] || options.for_update)
    {
        sql += ' FOR UPDATE';
    }
    else if (options['LOCK IN SHARE MODE'] || options.lock_share)
    {
        sql += ' LOCK IN SHARE MODE';
    }
    return new Text(sql, bind);
}

function tables_builder(tables)
{
    let sql = '', bind = [];
    let moreWhere = null;
    let first = true;
    if (typeof tables == 'string')
    {
        sql = tables;
        return { sql, bind, moreWhere };
    }
    else if (tables instanceof Text)
    {
        return { sql: tables.sql, bind: tables.bind, moreWhere };
    }
    for (const k in tables)
    {
        let jointype = 'INNER', table = tables[k], conds = null;
        if (table instanceof Array)
        {
            [ jointype, table, conds ] = table;
        }
        if (!first)
        {
            sql += ' ' + jointype.toUpperCase() + ' JOIN ';
        }
        let more_on;
        if (table instanceof Pg_Values)
        {
            sql += '(VALUES ';
            let i = 0;
            for (const row of table.rows)
            {
                sql += (i > 0 ? ', (' : '(') + table.keys.map(() => '?').join(', ')+')';
                table.keys.forEach(k => bind.push(row[k]));
                i++;
            }
            sql += ') AS '+k+'('+table.keys.join(', ')+')';
        }
        else if (table instanceof Text)
        {
            sql += '(' + table.sql + ') ' + k;
            table.bind.forEach(v => bind.push(v));
        }
        else if (typeof table == 'object')
        {
            // Nested join, `k` alias is ignored
            let subjoin = tables_builder(table);
            if (subjoin.moreWhere)
            {
                more_on = subjoin.moreWhere;
            }
            if (Object.keys(table).length > 1)
            {
                sql += "("+subjoin.sql+")";
            }
            else
            {
                sql += subjoin.sql;
            }
            subjoin.bind.forEach(v => bind.push(v));
        }
        else
        {
            sql += table + ' ' + k;
        }
        conds = where_builder(conds);
        if (more_on)
        {
            if (!conds.sql)
                conds = more_on;
            else
            {
                conds.sql += ' AND ' + more_on.sql;
                more_on.bind.forEach(v => conds.bind.push(v));
            }
        }
        if (!first)
        {
            sql += ' ON ' + (conds.sql || '1=1');
            conds.bind.forEach(v => bind.push(v));
        }
        else
        {
            // Бывает удобно указывать WHERE как условие "JOIN" первой таблицы
            moreWhere = conds.sql ? conds : null;
            first = false;
        }
    }
    return { sql, bind, moreWhere };
}

function where_in(key, values, result, bind, for_where)
{
    if (values[0] instanceof Array)
    {
        // only for WHERE: [ '(a, b)', [ [ 1, 2 ], [ 3, 4 ], ... ] ]
        if (!for_where)
        {
            throw new Error('IN syntax can only be used inside WHERE');
        }
        result.push(key + ' in (' + values.map(vi => '('+vi.map(() => '?').join(', ')+')') + ')');
        values.forEach(vi => vi.forEach(v => bind.push(v)));
    }
    else if (!for_where)
    {
        if (values.length > 1)
        {
            throw new Error('IN syntax can only be used inside WHERE');
        }
        if (values[0] instanceof Text)
        {
            push_text(result, bind, new Text(key+' = '+values[0].sql, values[0].bind));
        }
        else
        {
            result.push(key+' = ?');
            bind.push(values[0]);
        }
    }
    else
    {
        // [ field, [ values ] ]
        let non_null = values.filter(vi => vi != null);
        let has_null = values.length > non_null.length;
        if (non_null.length > 0)
        {
            result.push(
                key+' in (' + non_null.map(() => '?').join(', ') + ')' +
                (has_null ? ' or '+key+' is null' : '')
            );
            non_null.forEach(v => bind.push(v));
        }
        else if (has_null)
        {
            result.push(key+' is null');
        }
    }
}

function push_text(where, bind, v)
{
    if (v instanceof Text)
    {
        where.push(v.sql);
        for (let i = 0; i < v.bind.length; i++)
            bind.push(v.bind[i]);
    }
    else
        where.push(v);
}

// fields: one of:
// - string: 'a=b AND c=d'
// - array: [ 'a=b', [ 'a=? or b=?', 1, 2 ], [ 'a', [ 1, 2 ] ] ]
// - object: { a: 1, b: [ 1, 2 ], 'a = b': [], '(a, b)': [ [ 1, 2 ], [ 2, 3 ] ], 'c=? or d=?': [ 2, 3 ] }
//   - key does not contain '?', value is a scalar or non-empty array => (key IN ...)
//   - key does not contain '?', value is an empty array => just (key)
//   - key contains '?', value is a scalar or non-empty array => (key) with bind params (...value)
//   - key is numeric, then value is treated as in array
function where_or_set(fields, for_where)
{
    if (typeof fields == 'string')
    {
        return { sql: fields, bind: [] };
    }
    const where = [], bind = [];
    for (let k in fields)
    {
        let v = fields[k];
        if (/^\d+$/.exec(k))
        {
            if (!(v instanceof Array))
            {
                push_text(where, bind, v);
                continue;
            }
            else if (v.length == 0 || typeof v[0] !== 'string')
            {
                // invalid value
                continue;
            }
            else if (v.length == 1)
            {
                // [ text ] or just text
                push_text(where, bind, v[0]);
            }
            else if (v[0].indexOf('?') >= 0)
            {
                // [ text, bind1, bind2, ... ]
                // FIXME: check bind variable count
                where.push(v[0]);
                for (let i = 1; i < v.length; i++)
                    bind.push(v[i]);
            }
            else
            {
                // [ field, [ ...values ] ]
                if (v.length > 2)
                {
                    throw new Error('Invalid condition: '+JSON.stringify(v));
                }
                v[1] = v[1] instanceof Array ? v[1] : [ v[1] ];
                where_in(v[0], v[1], where, bind, for_where);
            }
        }
        else
        {
            if (!(v instanceof Array))
            {
                v = [ v ];
            }
            if (k.indexOf('?') >= 0 || v.length == 0)
            {
                // { expr: [ bind ] }
                // FIXME: check bind variable count
                where.push(k);
                for (let i = 0; i < v.length; i++)
                    bind.push(v[i]);
            }
            else
            {
                where_in(k, v, where, bind, for_where);
            }
        }
    }
    if (!for_where)
    {
        // SET
        return { sql: where.join(', '), bind };
    }
    // WHERE
    return { sql: where.length ? '('+where.join(') and (')+')' : '', bind };
}

function where_builder(where)
{
    return where_or_set(where, true);
}

/**
 * Разбивает набор таблиц на основную обновляемую + набор дополнительных
 *
 * Идея в том, чтобы обрабатывать хотя бы 2 простые ситуации:
 * UPDATE table1 INNER JOIN table2 ...
 * UPDATE table1 LEFT JOIN table2 ...
 */
function split_using(tables)
{
    if (typeof tables == 'string')
    {
        return { what: { sql: tables, bind: [] }, using: null, moreWhere: null };
    }
    let first = null;
    let is_next_inner = true;
    let i = 0;
    for (let k in tables)
    {
        let t = tables[k];
        if (i == 0)
        {
            if (t instanceof Array && typeof(t[1]) != 'string')
            {
                throw new Error('Can only update/delete from real tables, not sub-select, sub-join or VALUES');
            }
            first = k;
        }
        else if (i == 1)
        {
            is_next_inner = !(t instanceof Array) || t[0].toLowerCase() == 'inner';
        }
        else
        {
            break;
        }
        i++;
    }
    let what, moreWhere;
    if (is_next_inner)
    {
        what = tables_builder({ [first]: tables[first] });
        delete tables[first];
        moreWhere = what.moreWhere;
        what.moreWhere = null;
    }
    else
    {
        what = tables_builder({ ["_"+first]: tables[first] });
        const cond = '_'+first+'.ctid='+(/^\d+$/.exec(first) ? tables[first] : first)+'.ctid';
        moreWhere = what.moreWhere
            ? { sql: what.moreWhere.sql+' AND '+cond, bind: what.moreWhere.bind }
            : { sql: cond, bind: [] };
        what.moreWhere = null;
    }
    return { what, using: Object.keys(tables).length > 0 ? tables : null, moreWhere };
}

function quote(v)
{
    if (v == null)
        return 'null';
    else if (v === true || v === false)
        return ''+v;
    else if (typeof v == 'object')
        v = JSON.stringify(v);
    else if (typeof v == 'number')
        return v;
    return pg_escape.literal(v);
}

// Встроить все bind пераметры, выраженные как ?, в строку.
// Почему? А потому, что в node-postgres, похоже, есть лимит числа bind переменных. После ~30000 он сваливается.
// FIXME: В postgresql есть оператор ?. Его надо научиться экранировать. Либо сразу строить запрос в строчку
// и не заниматься ерундой с подстановками.
function _inline(sql, bind)
{
    let i = 0;
    sql = sql.replace(
        /'(?:[^\']*|\'\')*'|"(?:[^\"]*|\"\")*"|(\?)/g,
        (m, m1) =>
        {
            if (!m1)
                return m;
            return quote(bind[i++]);
        }
    );
    return sql;
}

// dbh: Connection or pg.Client
async function select(dbh, tables, fields, where, options, format)
{
    let sql_text, calc_found_rows, found_rows;
    if (arguments.length == 2 || arguments.length == 3)
    {
        sql_text = tables instanceof Text ? tables : new Text(tables, []);
        format = fields;
    }
    else
    {
        if (options && options.calc_found_rows)
        {
            calc_found_rows = true;
            fields = fields instanceof Array ? [ ...fields ] : [ fields ];
            fields.push('COUNT(*) OVER () \"*\"');
        }
        sql_text = select_builder(tables, fields, where, options);
    }
    let data = await dbh.query(sql_text.sql, sql_text.bind);
    if (calc_found_rows)
    {
        if (!data.rows.length)
            found_rows = 0;
        else
        {
            found_rows = data.rows[0]['*'];
            data.rows.forEach(r => delete r['*']);
        }
    }
    if (format & MS_LIST)
        data = data.rows.map(r => Object.values(r));
    else if (format & MS_COL)
        data = data.rows.map(r => Object.values(r)[0]);
    else
        data = data.rows;
    if (format & MS_ROW)
        data = data[0];
    return calc_found_rows ? [ found_rows, data ] : data;
}

async function insert(dbh, table, rows, options)
{
    if (!(rows instanceof Array))
    {
        rows = [ rows ];
    }
    if (!rows.length)
    {
        return null;
    }
    const keys = Object.keys(rows[0]);
    let sql = 'insert into '+table+' ('+keys.join(', ')+') values ';
    let i = 0;
    for (const row of rows)
    {
        let j = 0;
        sql += (i > 0 ? ', (' : '(');
        for (let k of keys)
        {
            if (j > 0)
                sql += ', ';
            if (row[k] == null)
                sql += 'default';
            else if (row[k] instanceof Text)
                sql += row[k].toString();
            else
                sql += quote(row[k]);
            j++;
        }
        sql += ')';
        i++;
    }
    if (options)
    {
        if (options.upsert)
        {
            sql += ' on conflict '+
                (options.upsert instanceof Array
                    ? '('+options.upsert.join(', ')+')'
                    : (typeof options.upsert == 'string' ? options.upsert : '(id)'))+
                ' do update set '+
                (options.upsert_fields || keys).map(k => `${k} = excluded.${k}`).join(', ');
        }
        else if (options.ignore)
        {
            sql += ' on conflict '+
                (options.ignore instanceof Array
                    ? '('+options.ignore.join(', ')+')'
                    : (typeof options.ignore == 'string' ? options.ignore : '(id)'))+
                ' do nothing';
        }
        if (options.returning)
        {
            sql += ' returning '+options.returning;
            return (await dbh.query(sql)).rows;
        }
    }
    return await dbh.query(sql);
}

async function _delete(dbh, table, where, options)
{
    where = where_builder(where);
    const split = split_using(table);
    if (split.using)
    {
        split.using = tables_builder(split.using);
    }
    let sql = 'delete from '+split.what.sql+
        (split.using ? ' using '+split.using.sql : '')+
        ' where '+(where.sql || '1=1')+(split.moreWhere ? ' and '+split.moreWhere.sql : '');
    let bind = [ ...split.what.bind, ...where.bind, ...(split.moreWhere ? split.moreWhere.bind : []) ];
    if (options && options.returning)
    {
        sql += ' returning '+options.returning;
        return (await dbh.query(sql, bind)).rows;
    }
    return await dbh.query(sql, bind);
}

async function update(dbh, table, set, where, options)
{
    set = where_or_set(set, false);
    where = where_builder(where);
    const split = split_using(table);
    if (split.using)
    {
        split.using = tables_builder(split.using);
    }
    let sql = 'update '+split.what.sql+' set '+set.sql+
        (split.using ? ' from '+split.using.sql : '')+
        ' where '+(where.sql || '1=1')+(split.moreWhere ? ' and '+split.moreWhere.sql : '');
    let bind = [
        ...split.what.bind,
        ...set.bind,
        ...(split.using ? split.using.bind : []),
        ...where.bind,
        ...(split.moreWhere ? split.moreWhere.bind : [])
    ];
    if (options && options.returning)
    {
        sql += ' returning '+options.returning;
        return (await dbh.query(sql, bind)).rows;
    }
    return await dbh.query(sql, bind);
}

function values(rows)
{
    return new Pg_Values(Object.keys(rows[0]), rows);
}

class Pg_Values
{
    constructor(keys, rows)
    {
        this.keys = keys;
        this.rows = rows;
    }
}

class Text
{
    constructor(sql, bind)
    {
        this.sql = sql;
        this.bind = bind || [];
    }

    toString()
    {
        return _inline(this.sql, this.bind);
    }

    concat(text)
    {
        return new Text(this.sql+text.sql, [ ...this.bind, ...text.bind ]);
    }
}

class ConnectionBase
{
    async select(tables, fields, where, options, format)
    {
        return arguments.length <= 2
            ? await select(this, tables, fields)
            : await select(this, tables, fields, where, options, format);
    }

    async insert(table, rows, options)
    {
        return await insert(this, table, rows, options);
    }

    async update(table, set, where, options)
    {
        return await update(this, table, set, where, options);
    }

    async delete(table, where, options)
    {
        return await _delete(this, table, where, options);
    }
}

ConnectionBase.prototype.HASH = MS_HASH;
ConnectionBase.prototype.LIST = MS_LIST;
ConnectionBase.prototype.ROW = MS_ROW;
ConnectionBase.prototype.COL = MS_COL;
ConnectionBase.prototype.VALUE = MS_VALUE;
ConnectionBase.prototype.select_builder = select_builder;

// Обёртка PostgreSQL-подключения
// Автоматически переподключается при отвале
class Connection extends ConnectionBase
{
    constructor(config)
    {
        super();
        this.config = config;
        this.init_connect = [];
        this.in_transaction = null;
        this.transaction_queue = [];
        this.quote = quote;
    }

    handleError(dbh, e)
    {
        // Проверяем, что в нас не кидается ошибкой старое подключение к БД
        if (dbh == this.dbh)
        {
            console.warn(e);
            console.warn('Database connection dropped. Reconnecting');
            this.dbh = null;
            this.connection_lost = true;
            this.connect();
        }
    }

    getConnection()
    {
        return this.dbh;
    }

    async runWhenConnected(cb)
    {
        if (this.dbh)
        {
            await cb(this);
        }
        this.init_connect.push(cb);
    }

    dontRunWhenConnected(cb)
    {
        this.init_connect = this.init_connect.filter(c => c != cb);
    }

    async connect()
    {
        if (this.dbh)
        {
            return this.dbh;
        }
        let retry = this.config.retry || 30;
        // eslint-disable-next-line no-constant-condition
        while (true)
        {
            try
            {
                let dbh = this.dbh = new pg.Client(this.config);
                await this.dbh.connect();
                for (const cb of this.init_connect)
                {
                    await cb(this);
                }
                dbh.on('error', e => this.handleError(dbh, e));
                return this.dbh;
            }
            catch (e)
            {
                this.dbh = null;
                console.warn(e);
                console.warn('Trying to connect again in '+retry+' seconds');
                await new Promise((r, j) => setTimeout(r, retry*1000));
                if (this.dbh)
                {
                    return this.dbh;
                }
            }
        }
    }

    async begin()
    {
        while (this.in_transaction)
        {
            // Если уже кто-то активен - ждём его
            await new Promise((resolve, reject) => this.transaction_queue.push(resolve));
        }
        this.in_transaction = new Transaction(this);
        await this._query('begin');
        return this.in_transaction;
    }

    async txn(cb)
    {
        let r;
        const txn = await this.begin();
        try
        {
            r = await cb(txn);
            await txn.commit();
        }
        catch (e)
        {
            await txn.rollback();
            throw e;
        }
        return r;
    }

    async query(sql, bind)
    {
        if (sql.length == 5 && sql.toLowerCase() == 'begin')
        {
            throw new Error('Do not use transactions in asynchronous code directly!');
        }
        while (this.in_transaction)
        {
            // Если уже кто-то активен - ждём его
            await new Promise((resolve, reject) => this.transaction_queue.push(resolve));
        }
        if (!this.dbh)
            await this.connect();
        this.in_transaction = true;
        const r = await this._query(sql, bind);
        this.in_transaction = null;
        // Если есть ещё кто-то в очереди - пусть проходит
        this._next_txn();
        return r;
    }

    async end()
    {
        if (!this.dbh)
        {
            return;
        }
        while (this.in_transaction)
        {
            // Если уже кто-то активен - ждём его
            await new Promise((resolve, reject) => this.transaction_queue.push(resolve));
        }
        await this.dbh.end();
        this.dbh = null;
    }

    _next_txn()
    {
        this.in_transaction = null;
        const next = this.transaction_queue.shift();
        if (next)
            setImmediate(next);
    }

    async _query(sql, bind)
    {
        if (this.in_transaction && this.in_transaction !== true && this.connection_lost)
        {
            this.connection_lost = false;
            this._next_txn();
            throw new Error('Connection lost while in transaction');
        }
        this.connection_lost = false;
        sql = (bind && bind.length ? _inline(sql, bind) : sql);
        let start_time;
        try
        {
            if (this.config.log_queries)
            {
                start_time = Date.now();
            }
            const r = await this.dbh.query(sql);
            if (this.config.log_queries)
            {
                const tm = (Date.now()-start_time)/1000;
                if (!this.config.slow_query_time || tm > this.config.slow_query_time)
                {
                    console.log('> pid='+process.pid+' '+tm.toFixed(3)+' '+sql);
                }
            }
            return r;
        }
        catch (e)
        {
            // в postgresql надо откатывать всю транзакцию при любой ошибке
            // не падать, если в процессе выполнения запроса отвалилось подключение
            if (this.dbh)
            {
                if (this.in_transaction)
                {
                    if (this.in_transaction === true)
                        this._next_txn();
                    else
                        await this.in_transaction.query('rollback');
                }
                else
                {
                    if (this.config.log_queries)
                        console.log('> rollback');
                    await this.dbh.query('rollback');
                }
            }
            e.message = 'Error running query: '+sql+'\n'+e.message;
            throw e;
        }
    }
}

// Интересная обёртка для транзакций - позволяет использовать транзакции в асинхронном коде в одном подключении БД
class Transaction extends ConnectionBase
{
    constructor(dbh)
    {
        super();
        this.dbh = dbh;
        this.nested = 0;
        this.rolled_back = false;
    }

    async begin()
    {
        // Вложенная транзакция
        // SAVEPOINT пока не поддерживаем - просто делаем вид, что началась вложенная транзакция
        this.nested++;
        return this;
    }

    async txn(cb)
    {
        return await cb(this);
    }

    async commit()
    {
        if (this.nested > 0)
        {
            this.nested--;
        }
        else
        {
            await this.query('commit');
        }
    }

    async rollback()
    {
        if (!this.rolled_back)
        {
            await this.query('rollback');
            this.rolled_back = true;
        }
        else if (this.nested > 0)
        {
            this.nested--;
        }
    }

    async query(sql, bind)
    {
        if (this.rolled_back)
        {
            return null;
        }
        // Здесь уже ждать никого не надо, т.к. если мы сюда попали - то уже дождались своей очереди априори
        const r = await this.dbh._query(sql, bind);
        if (sql.length == 6 && sql.toLowerCase() == 'commit' ||
            sql.length == 8 && sql.toLowerCase() == 'rollback')
        {
            this.dbh._next_txn();
        }
        return r;
    }
}

module.exports = {
    select_builder,
    where_builder,
    where_or_set,
    quote,
    quote_into: _inline,
    select,
    insert,
    delete: _delete,
    update,
    values,
    Text,
    Connection,
    MS_HASH,
    MS_LIST,
    MS_ROW,
    MS_COL,
    MS_VALUE,
};